Rotary piston compressor

ABSTRACT

A CIRCULAR PISTON COMPRESSOR HAVING A STATIONARY HOUSING WITH A TROCHOIDAL INNER BOUNDARY AND A ROTARY PISTON MOUNTED ON THE ECCENTRIC OF A SHAFT SO THAT ITS AXIAL CENTERLINE DESCRIBES A CIRCULAR PATH DURING ITS ROTATION. INLET APERTURES ARE PROVIDED IN THE END WALLS OR COVER OF THE HOUSING OR BOTH FOR ENTRY OF THE WORKING MEDIUM AND OUTLET APERTURES ARE PROVIDED IN THE FLANKS OF THE PISTON. A PASSAGE ADAPTED TO COMMUNICATE WITH THE OUTLET APERTURE OCCUPIES VIRTUALLY THE INSIDE DIAMETER OF THE ECCENTRIC AND DIAMETER SPIRALLY IN THE PIN TOWARDS THE OUTLET FOR OUTLET OF THE COMPRESSED MEDIUM.

June 20, 1972 F. LUCK 3,671,153

ROTARY PISTON COMPRESSOR Filed Aug. 24, 1970 2 Sheets-Sheet 1 1 3 H II 3 Q F lg 1 3 I20 10 5 w [2b SG D June 20, 1972 F. LUCK 3,671,153

ROTARY PISTON COMPRESSOR Filed Aug. 24, 1970 2 Sheets-Sheet 3 AT7'aR/ KS United States Patent US. Cl. 418-61 4 Claims ABSTRACT OF THE DISCLOSURE A circular piston compressor having a stationary housing with a trochoidal inner boundary and a rotary piston mounted on the eccentric of 'a shaft so that its axial centerline describes a circular path during its rotation. Inlet apertures are provided in the end walls or cover of the housing or both for entry of the working medium and outlet apertures are provided in the flanks of the piston. A passage adapted to communicate with the outlet aperture occupies virtually the inside diameter of the eccentric and diminishes spirally in the pin towards the outlet for outlet of the compressed medium.

The invention relates to a circular piston compressor having a trochoidal inner boundary or surface of its stationary housing and a rotary piston mounted on the eccentric of a eccentric shaft, so that its axial centerline describes a circular path during its rotation.

Heretofore, circular piston compressors of the trochoidal type with slip engagement, as opposed to rotary piston compressors of that type, have not been known. In particular, the opinion has been held that in circular piston compressors, an unavoidable outlay for eccentric shaft and counterweights would outweigh the advantages afforded, and moreover that additional control members would be required.

The problem of concern is to avoid such additional control members and to make possible passage cross sections of adequate size, and in particular, to construct the outlet passage to equalize and diminish outlet shocks.

According to the invention, this problem is solved in the following manner. Intake apertures are provided in the end walls and/or cover of the housing, in a manner known per se, for entry of the working medium. For outlet of the compressed medium, apertures are present in the flanks of the piston and a passage is present in the eccentric and its pin. The passage in the eccentric occupying nearly its entire inside diameter, and constricting spirally in the eccentric pin towards the outlet.

Due to the spiral shape of the interior of the eccentric, the medium is set in a rotation superimposed on the motion of the eccentric. With this rotation it traverses the cylindrical outflow passage in the eccentric pin and flows out of the compression chamber without undesirable eddy formation.

The rotary motion in the outflow passage is maintained, though in attenuated form, over the period during which delivery of the medium ceases until the beginning of the next delivery impulse. Therefore, when the new delivery impulse begins, the medium does not have to be accelerated from rest. Instead, a translatory motion need merely be imposed as a component upon its tangential motion. The reduction of shock may be gauged by unlike differences in velocities before and during the delivery impulse under the old and new systems.

It is desirable that the spirally constricting inner chamber of the eccentric be arranged so that the part of the eccentric shell serving as a baflie wall for the medium "ice is increasingly thickened towards the end away from the inlet aperture and has a tongue-like projection continuing the spiral curve of the inner wall of the eccentric and forming a cushion space not participating in the flow of the medium.

This tongue-shaped projection suppresses parasite circulations in the inner chamber of the eccentric. The cushion space divided off by it, owing to the elasticity of its contents, damps the oscillations of medium caused by outlet shocks. The arrangement of the spiral baffle wall has the additional advantage that the kinetic energy of the medium flowing out in rotation is utilized towards the rotation of the shaft, thus reclaiming flow losses that would otherwise occur.

An important factor for effectiveness of the proposed eccentric chamber is the direction of flow of the entering medium. In fact, optimum conditions are present if the flow meets the anterior part of the inner boundary wall at as acute an angle as possible, so as not to radially approach the outlet in the eccentric pin. It is therefore desirable that, in the direction of rotation of the piston, the leading and trailing edges of the outlet apertures in the flanks of the piston be inclined in adaptation to the angle of the spiral wall of the eccentric chamber at its inlet opening.

The direction of flow may be further influenced by various arrangements of the outlet apertures in the piston. Thus the outlet apertures may, as known per se, be shifted out of the centers of the flanks of the piston in direction of rotation, that is, asymmetrically arranged. This changes the proportions of flow to be drawn respectively from the posterior and anterior parts of the working chamber in question, so that the flow direction in the outlet port of the piston is likewise modified.

A displacement of the outlet aperture into the leading part of the flank lends the flow vector a more tangential direction, and a displacement into the trailing part, a more radial direction.

The most favorable outlet arrangement will depend on the size and shape of the outlet aperture and on other factors.

In utilizing the arrangement described for high pressure ratios, where high temperatures of the medium occur, nozzles may be provided in the working chambers to inject cooling oil. To achieve a cooling elfect during the compression process, the nozzles may advantageously be arranged in the vicinity of the axial zones of the trochoids, either in the shell or in the end walls of the housing. At the same time, the cooling oil may serve to lubricate the sliding parts of the machine and help seal the working chambers.

An embodiment of the invention is represented in the accompanying drawing and will be described below in greater detail. In the drawing,

FIG. 1 shows an axial section of a circular piston compressor according to the invention,

FIG. 2 shows a radical section at the line IIII in FIG. 1,

FIG. 3 shows a partial cross section in the same plane with the rotary piston in a different position, and

FIG. 4 shows a partial cross section in the same plane with asymmetrical outlet apertures.

The stationary, multiply subdivided housing 1 of the machine, stepped up for example in a ratio of 2/3, with the housing being bounded by the trochoid 2, contains a suction passage 3 leading to the lateral intake apertures 4. In the housing a shaft 5 is mounted on bearings 6 and 7. The shaft 5 is composed of drive pin 5a, hollow eccentric 5b, and tubular pins 5c, through which the compressed medium is carried off. The piston 8 is mounted on the eccentric 5b. In its flanks, it has outlet apertures 9 through which the compressed medium is forced into the chamber of the eccentric 512 by way of the entrance 10 in the shelll of the eccentric. The axial centerline of piston 8 travels together with the eccentric 5b in a circular path in the direction of the arrow 11, while piston 8, with the aid of a transmission 12, ratio 2/ 3, consisting of an internal gear 12a fixed to the piston 8 and a pinion 12b fixed to the housing, executes an additional rotation about its centerline. The imbalance due to the eccentric position of piston 8 is corrected by counterweights 13, 14 and by the thickening of the wall of the eccentric 5b.

In FIG. 2, the piston 8 is in the position of incipient outlet of medium from the working chamber 15. The flow of medium forced out through the outlet aperture 9 is indicated by the arrow 16. Subsequently, it is deflected by the spiral wall 5b of the eccentric and the adjoining tongue-shaped projection 17, and enters the eccentric pin 50 tangentially. The space 5e formed on the side of the eccentric at the left of the drawing, between the entrance 10 and the tongue-shaped projection 17, is not in the flow field and so acts merely as a cushion.

:FIG. 3 shows another position of the rotating parts. The eccentric 5b has rotated onward through 60, while the piston 8 has revolved 40 back relative to the eccentric 5 and 20 forward relative to the housing 1, thus reaching top dead center, where delivery ceases and the outlet aperture 9 closes. The compressed medium that has flowed into the hollow pin 5c of the eccentric assumes a pure rotary motion, which is maintained with decreasing intensity by the kinetic energy imparted until the new delivery impulse sets in. The proper rotation of the pin may here be disregarded, as it is only the relative velocity that counts.

FIG. 4 shows the modification with outlet apertures 9 in piston 8 arranged asymmetrically; specifically the apertures are placed in the leading portion of the flank 8a of the piston. The entrance 10 in eccentric 5b has suffered the like displacement, so that the same outlet aperture is still present in the same piston position. The position of the piston in FIG. 4 is the same as in FIG. 2. The flow direction in the outlet aperture 9 is indicated by the arrow 18. The curvature of this arrow means that the delivery is eflFected predominantly from the posterior, enlarged portion 15a of the working chamber 15. In other words, the flow must be more tangentially directed. A more graphic representation of this fact is difficult because in the present examples, the flow has already been deflected by the edge 5 of the eccentric.

I claim:

-1. A circular piston compressor having a stationary housing with a trochoidal inner boundary and a shaft including an eccentric and a pin therefor and having a rotary piston mounted on'the eccentric so that the axial centerline of the piston describes a circular path during the rotation thereof; the housing having intake apertures therein for entry of the working medium, the piston flanks having outlet apertures and the eccentric and its pin having a passage therethrough adapted to communicate with said outlet apertures, the passage substantially occupying the full interior of the eccentric and diminishing spirally in the direction of rotation of the piston in radial section and funnel-fashion in the direction of exit flow of the medium in axial section.

2. A rotary piston compressor in accordance with claim 1 wherein the leading and trailing edges, in the direction of rotation of the piston, of the outlet apertures in the flanks of the piston, are slanted in adaptation to the angle of the spiral wall of the eccentric chamber at its entrance.

3. A circular piston compressor in accordance with claim 1, wherein the outlet apertures codetermining the flow direction of the medium in the flanks of the piston are arranged asymmetrically, that is, in one of the leading and trailing parts of the flanks of the piston.

4. A circular piston compressor having a stationary housing with a trochoidal inner boundary and a shaft including an eccentric and a pin therefor and having a rotary piston mounted on the eccentric so that the axial centerline of the piston describes a circular path during the rotation thereof, the housing having intake apertures therein for entry of the working medium, the piston flanks having outlet apertures and the eccentric and its pin having a passage therethrough adapted to communicate with said outlet apertures, the passage occupying virtually the inside diameter of the eccentric and diminishing spirally in the pin toward the apertures for outlet of the compressed medium, part of the eccentric wall serving as baffle for the medium being increasingly thickened toward the side away from the entrance and having a tongue-shaped projection continuing the spiral curve of the eccentric wall, and the projection forming a cushion space not participating in the flow of the medium.

References Cited UNITED STATES PATENTS CARLTON R. CROYLE, Primary Examiner R. E. GLUCK, Assistant Examiner US. Cl. X.R. 

